demonstrations:liquid_nitrogen_freezing_fruit
Liquid Nitrogen Freezing Fruit
Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff
Categories: Liquid Nitrogen
Alternative titles: Cryogenic Fruit Shattering
Summary
When fruit such as a strawberry or berry is submerged in liquid nitrogen, the water inside its cells freezes almost instantly. This rapid freezing makes the fruit rigid and brittle, so when struck with a hammer or mallet, it shatters instead of squishing.
Procedure
- Put on safety glasses and cryogenic gloves.
- Place a piece of fruit (e.g., strawberry, blueberry, or grape) into a container of liquid nitrogen.
- Leave it submerged for several minutes until frozen solid.
- Using tongs, remove the fruit and place it on a sturdy surface.
- Strike the fruit with a hammer or mallet to demonstrate its brittle, shattered texture.
- (Optional) Record the demonstration with a high-speed camera to capture the shattering effect in detail.
Links
LIQUID NITROGEN VS FRUIT | Brothers Do Science: In The Lab - Oli White:
Cryoshattering Fruit - ChefSteps:
Variations
- Try different types of fruit (apple slices, banana pieces, or grapes) to compare textures when frozen.
- Use leafy vegetables (like lettuce or spinach) to show how they crumble when frozen.
- Compare the crushing of frozen fruit to unfrozen fruit to highlight the difference.
Safety Precautions
- Safety glasses required.
- Wear cryogenic gloves when handling liquid nitrogen and frozen fruit.
- Use tongs to remove fruit from liquid nitrogen - never touch it directly.
- Only strike fruit on a stable, non-breakable surface.
- Do not eat fruit until fully warmed to room temperature.
- Ensure liquid nitrogen is handled only in a well-ventilated area.
Questions to Consider
- Why does the fruit shatter instead of squish when frozen with liquid nitrogen?
- What happens to the water inside the fruit’s cells during rapid freezing?
- How does this relate to why frozen fruits at home sometimes feel mushy when thawed?
- How do industrial freeze-drying or cryopreservation techniques use similar principles?
- What does this experiment teach us about states of matter and the effects of temperature on materials?